Thousands of people could potentially be facing larger energy bills after a decision from a major water supplier to cease softening water.

Affinity Water – which supplies large parts of Essex and Hertfordshire including parts of the borough of Brentwood, Ongar, Harlow and Uttlesford – says the specialised equipment to soften the water has now come to the end of its life.

It means its customers will be supplied with the “natural level of hardness that is common to the town and surrounding areas”. Affinity Water derives much of its supply from chalk acquirers and as such is some of the hardest in the UK.

But the decision to stop softening the water in the Saffron Walden area has been challenged. Saffron Walden Town Council believes that the removal of the water softener is contrary to an agreement signed by the then Borough Council of Saffron Walden and the Lee Valley Water Company.

When the borough council sold the water company to the then Lee Valley Water Company – which has subsequently been assimilated into Affinity Water – it signed an agreement that water would be softened in Saffron Walden. This was done and residents paid an extra 10 per cent on their water bills for this service, although this extra charge has not been levied since 2014.

It is the town council’s belief that the 1964 agreement was in perpetuity and therefore Affinity Water is obligated to continue adding water softener to the water in Saffron Walden.

In a statement, the town council said: “Notwithstanding the agreement, the town council remains aggrieved that a company such as Affinity Water claims it cannot prioritise investment for water softening, whilst claiming that it remains committed to sustainability.

“Whilst the process of water softening may incur some carbon impact, the impact of greater draw on electricity – caused by furred kettles and other appliances – and the need to replace such equipment more frequently presumably has a greater impact on the environment.”

In an online advertisement for its customers in the Saffron Walden area to air any concerns, Affinity Water said it is unable to meet the ongoing additional costs that are required to continue to soften water.

It provides water to more than 3.6 million people across the south east of England – an area with naturally occurring hard water, and does not operate additional treatment to soften water anywhere else in its supply area.

In a statement, Affinity Water said: “We’ve not made this decision lightly.

“The challenges that climate change, demand for water and a growing population is placing on the whole water industry is immense. We really do have to make hard choices where investments are made to ensure long-term sustainable and resilient water supplies for our customers, whilst taking care of our environment.”